Latch mechanism



March 4, 1952 H. R. LINDERFELT 2,587,367

LATCH MECHANISM Filed Aug. 6, 1948 2 SHEETS-SHEET 1 JIIA'IIIIIIIIA iIIIIIIH II/l/I/I/II/I/l" Hal Raymond Linderfelf i 2 INVENTOR.

BY K

A 7' TORNE Y March 4, 1952 H. R. LINDERFELT LATCH MECHANISM 2SHEETS--SHEET 2 Filed Aug. 6, 1948 Hul Raymond Lihderfelt ATTORNEYPatented Mar. 4, 1.952

' LATCH: MECHANISM Hal Raymond Linderfelt, West Los, Angeles, Calif.,assig nor to Douglas. Aircraft Company, Inc., a corporation ofCalifornia ApplicationAugust: 6, 1948,. Serial No. 42,776

3 Claims. (Cl. 292--335) The present invention relates to; closures anddoors a d more. articularly to mnr vedm nisms for the automatic lockingagainst inadc vertent operation oi doo r latching mechanism in the openposition of the door,

The present invention relates to improvements in mechanism-s for lockinga door or closure latching handle in the unlatched position, of thelatch bolt or bolts to thereby hold the same in their retractedpositions within the door to prevent accidental or inadvertent movementof the handle to the position in which the latch bolt might beextendedand damage or mar the door jamb in the event of the closure of the door.

The present improvements are particularly adapted to aircraft doors ofthe flush or streamlined type in which a close and accurate fit of thedoor within its opening is desirable for aerodynamic reasons andparticularly so in the event of scaled doors in pressurized orsupercharged aircraft.

It is accordingly a principal object of th present invention to provideimproved door latching and locking mechanisms. A further object residesin the provision of automatic means for preventing the extension of thelatch bolts ofa closure or door at such times when the door is in otherthan its closed position. Another object resides in the provision ofrelatively simple, yet positive-acting and foolproof mechanism forblocking the latching movement of the bolt of a door when the same isnot in the closed position. Further objects of the present inventionreside in improvements in the general arrangement and relationship ofthe interlocking mechanism with respect to the latching mechanism of adoor, as well as in detailed improvements of the respective elements.

Other objects andadvantages of the present invention will occur to thoseskilled in the art after reading the following description taken inconjunction with the accompanying drawings, forming a part hereof,inwhich:

Fig. l is an elevational view of a door to which the improved mechanismhas been applied;

Fig. 2 is a detail view of the improved mechanism in the unlatched openposition ofthe door;

Fig. 3 is a cross-sectional elevational view of the mechanism of Fig. 2as taken along the.lines 3- 3 thereof;

Fig. 4 is a sectional plan view of the mechanism in both the open andclosed positions of the door; and

Fig. 5 is a similar vie-w of a portion of the mechanism of Fig. 2, inthelatched closed .position of the door.

Referring now to Fig. 1, the numeral 7 represents a wall or enclosurewhich may be the interior surface oi the wall of an aircraft. This wallhas an opening therein, as defined by the jamb 28, within which there isdisposed a closure or door 8, which. door is preferably mounted upon thehinges 9 for movements between its opened and closed positions. Thenumeral It in Fig. 1 indicates the base plate or portion of. a housingI8 for the improved mechanism of the present invention, which housingand mechanism is shown in greater detail in the remaining figures.

Referring more particularly to Figs. 2 and 3, it will be noted that thebase plate 10 is rabbetted or-recessed on its outer face toreceive theouter sheet or skin of the door to which the flange of the base portion[8 is attached through its holes ltd, and the holes 8a of the doorsheet, as by the rivets or other fastening. means H. A major portion ofthe improved mechanism is housed within the housing or cover l8 which issuitably bored, together with the base plate In and the cover sheets ofthe door, to rotatably support .a handle shaft 12, having an internalhandle I3 and an external handle I3a fixedto the inner and outerterminals thereof, respectively. A latch stop element MisfiXedlyattached to the shaft [2 in such manner that it-rotates with the shaftas the handles l3 and I3a are manually rotated. This element 14 has anextended por tion bifurcated at Mb to which the roller I5 is pivoted atMa.

The handle assembly l2-l3|4 etc. is resiliently heldin either one of twoalternate positions by means of a snap-action spring toggle rod [6 whichis pivotally attached .to the latch stop element M. by means of thepivot pin H. The toggle rod I6 is guided for reciprocationat its outerterminal through the apertured guide or pillow block 30, which in turnis pivotally mounted upon the shaft 3l fo r partial rotation or rockingwithin suitably, b ored portions formed in the base plate I and thehousing cover I81. Inasmuch as the pivot 11 is e'ccentrically, disposedwith respect ,tothe. axis of the handle shaft, l2 and the spring .29,which is sleeved upon the rod [6, is continually under. compression, thepivot I1 is at all times urged away from the pivot shaft 3|.Accordingly, as the handle shaft I'Zis rotated past the dead centerline,joining the axes of shafts I 2 and 3f. the spring, 29 in extending thedistance between these pivots, causes. the latch stop element M, towhich itis pivotally at tached, to be quickly rotated to either of itsalternate limit positions. By referring to Fig. 2, it will be seen thata stop portion l 8a is integrally formed within the housing coverl8andin this figure the latch stop element [4 jhas'been rotated aboutshaft I2 as far as it can go in the counterclockwise dire'ction. Thisposition of the. toggle rod I6 and its pivotal. connection 1|! to thelatch Stop element 14 to hevri ht oithehandlelshaft l2 corresponds tohat in wh ch the. .latchingtelev inents 40 (Fig. 1') of the door a arein their ret-racted or unlatched positions, as will be hereinafter morefully explained.

The latch stop element I4 is provided with a bifurcated portion I4bwithin which the roller I5 is mounted for rotation upon the pivot pinMa. The roller I5 is positioned with respect to the axis of the handleshaft I2 such that in one of the said alternate or limit positionso-fthe handle I3, the end of the projecting portion of the element I4engages the above mentioned stop or detent I8a forming an integral partof the cover I8. In the other of said alternate limit positions of thehandle I3, corresponding to the extended position of the latches 40, inwhich the door is latched to the jamb 28, the roller I5 will engage theother endof the same detent portion I300, as shown in Fig. 5. The handleI3 can, however, only rotate the latching mechanism into this latchedposition of the door when the door is in the closed position, and thelatch stop element I4 is freed or released by the automatic interlockingmechanism, and more particularly by the lockingv or blocking element 25,about to be described.

The blocking element 20 is pivotally mounted for rocking movementswithin the transverse plane of the roller I5, and that of the latch stopelement I4 by which the roller is carried, being .journaled at itspivotal terminals within the base plate In and the housing I8. Theelement I4 is provided with a detent or recess I40 into which theblocking element 20 is adapted to fit. This rockable lock member 20extends through the cover I8 and is attached by the screw is to a lever2|. This lever 2| is pivotally connected to a push-pull rod 24 by meansof the pivot pin 22 and is connected at its lower free terminal by thetension spring 23 to the internal stifiening channel 81) at the hookedsprin terminal 23a; thereby tending to continually urge the lever 2I inthe counter-clockwise direction into the position shown in Fig. 2. Inthis position the pushpull rod 24 extends toward the right, or towardthe jam 28 of the door, and in this same position the locking element 20is concurrently urged upwardly against the roller E5.

The spring 23 normally holds the locking element 20 in engagement withthe detent i4a and against the roller I5 unless the tension of thisspring is overcome by the automatic release means which is provided inthe form of a bell crank lever 25, pivotally mounted at 25c upon the lug8c of the door 8, the bell crank carrying at its outer terminal apivoted roller 25. -As more clearly shown in Fig. 4, the wall portion isprovided with a bevelled jam 28 which has formed thereon the cam orprojection 21. This cam is engaged by the roller 26 as the door is movedfrom its full line open position A into the broken line closed positionof the door as indicated at B. It will be noted that as the roller 25strikes the end face of the cam 21 (as the door is closed) the bellcrank member 25 is caused to be rotated in the counter-clockwisedirection as viewed in the plan section of Fig. 4. The push-rod 24 isconcurrently moved to the left causing the attached lever 2I to berocked or moved into the position indicated by the construction lines inFig. 5, in which the locking element 2|] is rotated in the clockwisedirection downwardly out of the path or orbit of the projecting portionof the latch stop element I4 and the roller I5.

The mechanism for actuating the bolts or latches 40 for the door isoperated by means of the cable drum 32 which is fixedly attached to thehandle shaft I2 to rotate therewith. An endless cable 33 extends aroundthe drum 32 as well as around a centrally disposed and somewhat largerdiameter drum 34 pivotally mounted upon the pivot 35. Constructed andarranged to rock with the drum 34 are the bridle linkages 3B and 31which are attached to push-pull cables or other flexible means 38 guidedwithin the sheaths or tubes 39 and having attached at their outerterminals the latch bolts 40. It will accordingly be seen that as eitherhandle I3, or I30, is rotated the cable 33 causes concurrent rotation ofthe central drum 34, either pushing or pulling the flexible means 38 toextend or retract the latch bolts -40.

The operation of the door latching control mechanism and the automaticinterlocking or blocking lock device is as follows:

With the door 8 in its closed position against the jamb 28 of the Wall 7the roller 26 is in the deflected position toward the door as shown inthe broken line position B of Fig. 4 and the push rod 24 and.attached'lever 2| are also moved toward the lert causing the block Zu tobe moved into the position shown in Fig. 5 out of the path of the proecting portion'of the latch stop element I4 and the roller I5.Accordingly, in the closed and latched position of the door, the elementI4 will be in the position shown in Fig. 5 and the position of theinterlocking mechanism in the closed position of the door will be thatshown in this same figure in which the block 2i! is out of the path ofthe element I4 and the roller l5. In this closed and latched position ofthe door and its mechanism as shown in Fig. 5, it is possible to rotatethe handle I3 (or the other handle I3a) downwardly or in thecounter-clockwise direction in Fig. 5 until the projectin portion of theelement I4 strikes the stop Isa, it being only necessary to overcomethecompression in the spring 23 of the quick-acting toggle rod assemblyI5. During this rotation of the handle shaft 12, the sheave or drum 32,and its engaged cable 33, cause rotation of the door control mechanismto thereby retract the latch bolts 45. The element I4 and the roller I5,when the latch bolts are fully retracted, assume the position shown inFig. 2 with the aid of the toggle rod I6 and as the door is then pushedopen and the roller 26 rolls oil the end of the cam 27, the tensionspring 23 causes the lever 2 l to be rotated toward the right or in theclockwisedirection as viewed in Figs. 2 and 5, and the'blocking element2!] moves into the detent or recess I40 in the latch stop element I4,blocking any clockwise movement of the element I4, the roller I5 and theattached shaft I2. The door latch control mechanism is therefore lockedin its unlatched condition as long as the door is in any other than itsfully closed position as determined by the engagement or disengagementof the roller 25 and the cam element 21 on the jamb 28. Accordingly, itis not possible to close the door with the latch bolts 40 in theirextended positions.

Other forms and modifications of the present invention both in respectto its general arrangement and the details of its respective parts,which may become apparent to those skilled in the art after reading thisdescription, are all intended to fall within the scope and spirit of thepresent invention as more particularly defined in the appended claims.

1. Latch mechanism for a door comprising a manually rotatable latchoperating means, a bellcrank lever pivotally mounted upon the door uponan axis substantially parallel to the plane of said door, a first arm ofsaid bell-crank lever rotatable into a block position in which itprevents man-ual operation of said latch operating means, resilientmeans attached to said bellcrank lever urging said first arm portioninto said blocking position, stop means fixedly carried by said door forengagement by said manually rotatable latch operating means for definingthe extreme limits of movement thereof, springpressed toggle meanspivotally interconnecting said manually rotatable latch operating meanswith said door for snap-action movement of said manually rotatable latchoperating means into either of said limit positions whenever manuallyrotated past an intermediate position and released at such position, andjamb engaging means including a pivotally mounted roller operativelycarried by a second arm of said bell-crank lever arranged in such mannerthat in the closed position of said door, said jamb engaging meansimparts rotation to said bell-crank lever thereby overcoming saidresilient means and rotating said bell-crank lever into the unblockingposition of said first arm portion in which said latch operating meansis free to be manually actuated into either its latch extended or latchretracted limit position.

2. Automatic latch blocking means for a door installation including ahingedly mounted door and a wall having a jamb portion defining anopening arranged to be closed by said door, comprising bolt meansmovably mounted upon said door for latching engagement with said jambportion, manually rotatable actuating means operatively connected tosaid bolt means for the extension and retraction of said bolt means, aprojecting portion carried by said rotatable bolt actuating means, stopmeans fixedly carried by said door for engagement by said projectingportion at the extreme limit positions of retraction and extensionmovements of said rotatable bolt actuating means, spring-pressed togglemeans pivotally interconnecting said rotatable actuating means with saiddoor for snap-action movement of said rotatable bolt actuating meansinto either of said limit positions, blocking means operativelyengageablewith said rotatable bolt means for blocking the rotationthereof, strike 6 means fixedly carried by said jamb portion, abell-crank lever pivotally mounted upon said door on an axissubstantially parallel to the plane of said adjacent dopr surface, saidbellcrank lever pivotally connected to said blocking means and having aportion in engagementwith said strike means arranged in such manner thatupon closing of said door and engagement of said bell-crank lever withsaid strike means rotation is imparted to said bell-crank lever causingmovement of said blocking means into a position in which said manuallyrotatable bolt means is free for manual rotation into either one of saidlimit positions in which said bolt means may be extended or retracted.

3. ,Latch mechanism for a door installation including bolt means forlatching said door to its jamb, manually rotatable means for operatingsaid bolt means into either its extended or its retracted limitpositions, spring-biased toggle means operatively connected to saidmanually rotatable means for rotating said manually rotatable means intoeither one of said two limit positions upon release of said manuallyrotatable means, blocking means operatively engaging said vmanuallyrotatable means for blocking the rotation thereof, strike means carriedby said door jamb, a bell-crank lever pivotally mounted upon said doorupon an axis substantially parallel to the surface of said door, saidbell-crank lever pivotally connected to said blocking means and having acontacting portion engageable upon closing of said door with said strikemeans carried by said door jamb arranged in such manner that saidbell-crank is rotated thereby imparting movement to said blocking meansfor the freeing of said manually rotatable means in such manner thatsaid bolt means, may be extended or retracted manually in said closedposition of said door.

HAL RAYMOND LINDERFELT.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 281,458 Conner July 17, 18831,870,746 Pyle Aug. 9, 1932 1,904,970 Cook Apr. 18. 1933 1,996,865 HaagApr. 9, 1935

